DESCRIPTION: (Applicant's Abstract) This project represents an extension of the applicant's investigations of liver specific gene expression and hepatocyte progenitor cell activation. The applicant proposes to use the rat copper deficiency model developed by Reddy et al. where massive atrophy of pancreatic acini is associated with proliferation of ductal epithelial cells and the appearance in the pancreases of cells expressing liver specific genes and hepatocyte morphology. In preliminary studies with this model the applicant has observed epithelial cell proliferation and induction of hepatocyte specific genes characteristic of early stages of hepatocyte lineage progression. However, few if any of these cells progress to mature hepatocytes. This arrest of progression is associated with incomplete expression of liver enriched transcription factors that regulate expression of liver specific genes. The applicant has transplanted activated pancreatic epithelial cells into the livers of recipient rats and observed maturation of the transplanted cells into hepatocytes. Based on previous work and relevant preliminary studies the applicant's hypothesis is that gastrointestinal organs maintain a small pool of epithelial progenitor cells that can be activated to proliferate under certain pathophysiologic conditions and that a variety of factors regulate the gene expression program and differentiation potential in these cells. The applicant will investigate this hypothesis as pertains to hepatocyte progenitor cell lineage in the copper deficiency rat model using a combination of molecular and histochemical methods to identify genes involved in the activation of pancreatic epithelial progenitor cells to proliferate and differentiate along the hepatocyte lineage. The Specific Aims are: 1. To isolate candidate genes from the applicant's pancreatic activated epithelial cell cDNA library that are induced in the activated epithelial cells progressing along the hepatocyte lineage; 2. To identify known and novel genes that are induced by sequencing and to identify through the sequences functional nucleic acid and peptide domains; 3. To study the biological function of newly identified induced genes; 4. To transplant activated pancreatic epithelial progenitor cells into the livers of inbred rats or immunotolerant Alb-uPA transgenic mice to observe their proliferation and/or differentiation into hepatocytes.